16. Classify each statement as an observation, a law, or a theory.(a) The star closest to Earth is moving away from Earth athigh speed.(b) A body in motion stays in motion unless acted upon bya force.(c) The universe began as a cosmic explosion called theBig Bang.(d) A stone dropped from an altitude of 450 m falls to theground in 9.6 s.
Stellar evolution
We may see thousands of stars in the dark sky. Our universe consists of billions of stars. Stars may appear tiny to us but they are huge balls of gasses. Sun is a star of average size. Some stars are even a thousand times larger than the sun. The stars do not exist forever they have a certain lifetime. The life span of the sun is about 10 billion years. The star undergoes various changes during its lifetime, this process is called stellar evolution. The structure of the sun-like star is shown below.
Red Shift
It is an astronomical phenomenon. In this phenomenon, increase in wavelength with corresponding decrease in photon energy and frequency of radiation of light. It is the displacement of spectrum of any kind of astronomical object to the longer wavelengths (red) side.
16. Classify each statement as an observation, a law, or a theory.
(a) The star closest to Earth is moving away from Earth at
high speed.
(b) A body in motion stays in motion unless acted upon by
a force.
(c) The universe began as a cosmic explosion called the
Big Bang.
(d) A stone dropped from an altitude of 450 m falls to the
ground in 9.6 s.
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